October 1, 2023 # Belajar Bahasa C – Bouncing Balls

A child is playing with a ball on the nth floor of a tall building. The height of this floor above ground level, h, is known.

He drops the ball out of the window. The ball bounces (for example), to two-thirds of its height (a bounce of 0.66).

His mother looks out of a window 1.5 meters from the ground.

How many times will the mother see the ball pass in front of her window (including when it’s falling and bouncing?

## Three conditions must be met for a valid experiment:

• Float parameter “h” in meters must be greater than 0
• Float parameter “bounce” must be greater than 0 and less than 1
• Float parameter “window” must be less than h.

If all three conditions above are fulfilled, return a positive integer, otherwise return -1.

Note:
The ball can only be seen if the height of the rebounding ball is strictly greater than the window parameter.

## Examples:

``````- h = 3, bounce = 0.66, window = 1.5, result is 3

- h = 3, bounce = 1, window = 1.5, result is -1

(Condition 2) not fulfilled).``````

## Sample Test:

``````#include <criterion/criterion.h>

extern int bouncingBall (double h, double bounce, double window);
static void testequal(double h, double bounce, double window, int expected);

Test(bouncingBall, sampleTests) {
testequal(2, 0.5, 1.0, 1);
testequal(3, 0.66, 1.5, 3);
testequal(30, 0.66, 1.5, 15);
testequal(30, 0.75, 1.5, 21);
testequal(30, 0.4, 10, 3);
testequal(40, 0.4, 10, 3);
testequal(10, 0.6, 10, -1);
testequal(40, 1, 10, -1);
testequal(-5, 0.66, 1.5, -1);
testequal(5, -1, 1.5, -1);
testequal(4, 0.25, 1.0, 1);
}

static void testequal(double h, double bounce, double window, int expected) {
int actual = bouncingBall(h, bounce, window);
cr_assert_eq(actual, expected,
"for h = %f, bounce = %f, window = %f\n"
"expected %d, but got %d",
h, bounce, window,
expected, actual
);
}``````

## Solution

``````int bouncingBall(double h, double bounce, double window)
{
int s = 1;
if (h <= window || h < 0 || bounce < 0 || bounce >= 1)
s = -1;
else
{
h = h * bounce;
while (h > window)
{
s += 2;
h = h * bounce;
}
}

return s;
}
`````` #### Rajo Intan

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